Rotary screw pumps comprise, amongst other things, internal gear pumps and annular gear pumps in which a driving gearwheel runs eccentrically in the internal tooth system of an annular gear. Internal gear pumps, which are particularly suitable for providing high pressures, are used to deliver fluids, for example to deliver fuel to an internal combustion engine.
In the prior art, it is known to integrate internal gear pumps or annular gear pumps in an electronically commutated electric motor, with the rotor of the electric motor simultaneously being in the form of an annular gear of the internal gear pump or annular gear pump.
DE 10 2006 007 554 A1 describes a delivery pump which is integrated in an electric motor. The delivery pump comprises a first gearwheel and a second gearwheel. A delivery space is formed between the two gearwheels. The second gearwheel is mounted at its centre on a mandrel. The first gearwheel is an external gearwheel and forms the rotor, the second gearwheel is an internal gearwheel which is carried along in the eccentric center of the first gearwheel. The first gearwheel comprises glued-in permanent magnets which are arranged in a manner distributed over the circumference. External magnetic field generators generate a circulating rotationally changing field which results in direct motorized tracking of the rotor.
However, mounting of the annular gear, which has to adopt the drive torque of the electric motor, is problematical in configurations of this kind. At the same time, the hydraulic forces of the internal gear pump are transmitted to the stator and further to the pump housing.
EP 1 600 635 A2 describes an internal gear pump which has a pump section with an internal rotor which is formed with teeth on its outer periphery. An external rotor has teeth which are formed on its inner periphery. Both rotors are accommodated in a housing. The external rotor, which is in the form of an annular gear, is mounted by means of specially shaped additional components in this case.
The solutions known in the prior art for mounting the annular gear in an internal gear pump or in an annular gear pump have a mechanically complicated design and are therefore structurally elaborate, complex and expensive in terms of production.
Therefore, it is necessary to provide a simple and cost-effective solution for mounting an annular gear for a gear pump, in particular for an internal gear pump or an annular gear pump.